kernel: move z_is_thread_essential out of public kernel header

This is a private API to the kernel, so move out of kernel.h

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

include/zephyr/kernel.h

@@ -5950,8 +5950,6 @@ extern void z_init_static_threads(void);
 /**
  * @internal
  */
-extern bool z_is_thread_essential(void);
-
 #ifdef CONFIG_SMP
 void z_smp_thread_init(void *arg, struct k_thread *thread);
 void z_smp_thread_swap(void);

kernel/include/ksched.h

@@ -13,6 +13,8 @@
 #include <zephyr/tracing/tracing.h>
 #include <stdbool.h>
 
+bool z_is_thread_essential(void);
+
 BUILD_ASSERT(K_LOWEST_APPLICATION_THREAD_PRIO
 	     >= K_HIGHEST_APPLICATION_THREAD_PRIO);
 

tests/kernel/mem_protect/userspace/src/main.c

@@ -327,7 +327,7 @@ ZTEST_USER(userspace, test_write_kerntext)
 	/* Try to write to kernel text. */
 	set_fault(K_ERR_CPU_EXCEPTION);
 
-	memset(&z_is_thread_essential, 0, 4);
+	memset(&k_current_get, 0, 4);
 	zassert_unreachable("Write to kernel text did not fault");
 }
 

tests/kernel/threads/thread_apis/src/test_essential_thread.c

@@ -6,7 +6,10 @@
 #include <zephyr/ztest.h>
 #include <zephyr/kernel.h>
 #include <zephyr/kernel_structs.h>
+
+/* Internal APIs */
 #include <kernel_internal.h>
+#include <ksched.h>
 
 struct k_thread kthread_thread;
 struct k_thread kthread_thread1;